Strong circularly polarized luminescence from quantum dots/2D chiral perovskites composites

Chiral perovskites(CPs)have attracted enormous attentions since they have combined chirality and optoelectrical properties well which is promising in circularly polarized luminescence(CPL)application and of great importance for future spin-optoelectronics.However,there is a key contradiction that in chiral perovskites chirality distorts the crystal structure,leading to poor photoluminescence(PL)properties.Achieving the balance between chirality and PL is a major challenge for strong CPL from chiral perovskites.Differently,two-dimensional(2D)chiral perovskite has shown fascinating chiral induced spin selectivity(CISS)effect which can act as spin injector under ambient conditions.Here,we propose an effective strategy to achieve high CPL activity generated from quantum dots(QDs)by introducing 2D chiral perovskite as a chiral source,providing spin polarized carriers through the CISS effect.The as-synthesized QDs/CP composites exhibit dissymmetry factors(glum)up to 9.06×10^(−3).For the first time,we performed grazing incident wide angle X-ray scattering(GIWAXS)measurements,showing the chirality originates from the distorted lattices caused by the large chiral organic cations.Besides,time-resolved PL(TR-PL)measurements verify the enhanced CPL activity should be attributed to the charge transport between two components.These findings provide a useful method to achieve CPL in QDs/2D chiral perovskite heterojunctions which could be promising in spinoptoelectronics application.

Reversible phase transition for switchable second harmonic generation in 2D perovskite microwires

Highly efficient second-harmonic generation(SHG)has facilitated the development of nanophotonics and sustained promising applications,ranging from electro-optical modulation,frequency conversion,and optical frequency combs to pulse characterization.Although controllable SHG switching has been observed in nanophotonics structures and molecule systems,the relatively small SHG switching contrast impedes its application in switchable nonlinear optics.Herein,reversible phase transitions between glassy and crystalline states without material degradation are demonstrated based on solution-processed chiral perovskite microwire arrays.Breaking of lattice inversion symmetry and high crystallinity support efficient SHG in microwire arrays.By synergy of high-performance SHG and reversible phase transitions between glassy and crystalline states,reversible switching of SHG is demonstrated under facile conditions.The high SHG switching performances,together with a small footprint,pave the way toward the integration of switchable nonlinear devices based on microwire arrays.